One of the possible areas of tension might be on immigration and refugees, he said, as Trump criticized Pope Francis on the campaign trail in 2016 after the Pope celebrated Mass at the U.S.-Mexico border and urged everyone to pray for conversion of hearts over the suffering of forced migration.
Trump, who repeatedly promised to build a wall on the U.S.-Mexico border and make the Mexican government pay for it, said last February that the Pope was a "pawn" of the Mexican government and "is a very political person, I think he doesn't understand the problems our country has."
He also issued an executive order shutting down refugee admissions for four months at a time when Pope Francis has taken in refugees and U.S. bishops have called for the country to continue accepting refugees fleeing violence.
Meanwhile, there are other possible areas of collaboration between the U.S. and the Holy See, Hackett said in January, including on human trafficking, peace in the Middle East, a solution to the worsening crisis in Venezuela, and efforts to alleviate global poverty.
Pope Francis and President Trump met at the Vatican in May. According to a Vatican communique, they expressed satisfaction "for the good existing bilateral relations between the Holy See and the United States of America, as well as the joint commitment in favor of life, and freedom of worship and conscience."
During the "cordial discussions," the two expressed hope for peaceful collaboration between the government and the Catholic Church in the United States, that it may be "engaged in service to the people in the fields of healthcare, education and assistance to immigrants," the Vatican statement said.
The two leaders also exchanged views "on various themes relating to international affairs, the promotion of peace in the world through political negotiation and interreligious dialogue, with particular reference to the situation in the Middle East and the protection of Christian communities."